The study may involve the following evaluations: physical, neurological and psychological exams; ear, nose and throat evaluation; speech, language and swallowing evaluation; hearing test; eye examination; imaging studies (e.g., X-rays, ultrasound, MRI); developmental and behavioral assessment; rehabilitation evaluation with gait (walking) analysis; urinalysis, blood, and/or skin cell studies; sleep study; other consultations as required. A tissue sample (blood or cheek swab or skin biopsy) may be taken for genetic studies. To obtain a cheek swab, a small brush is rubbed against the inside of the cheek to wipe off some cells. For a skin biopsy, a small area of skin is numbed with a local anesthetic and a small circle of skin, usually about 1/8 inch, is removed with a biopsy tool. Parents may be asked to complete questionnaires about their child s growth and development, therapies, medications, sleep, development and behavioral concerns. They also may be asked to bring their child to NIH for follow-up visits every 6 months to 3 years, depending on the child s age. The purpose of these visits is to see how the child changes over time and to conduct additional tests.